Error compiling Cuda - expected primary-expression

问题

this program seems be fine but I still getting an erro, some suggestion?

Program:

#include "dot.h"
#include <cuda.h>
#include <cuda_runtime.h>
#include <stdio.h>

int main(int argc, char** argv)
{
    int *a, *b, *c;
    int *dev_a, *dev_b, *dev_c;
    int size = N * sizeof(int);

    cudaMalloc((void**)&dev_a, size);
    cudaMalloc((void**)&dev_b, size);
    cudaMalloc((void**)&dev_c, sizeof(int));

    a = (int *)malloc (size);
    b = (int *)malloc (size);
    c = (int *)malloc (sizeof(int));

    random_ints(a, N);
    random_ints(b, N);

    cudaMemcpy(dev_a, a, size, cudaMemcpyHostToDevice);
    cudaMemcpy(dev_b, b, size, cudaMemcpyHostToDevice);

    int res = N/THREADS_PER_BLOCK;
    dot<<< res, THREADS_PER_BLOCK >>> (dev_a, dev_b, dev_c);
    //helloWorld<<< dimGrid, dimBlock >>>(d_str);

    cudaMemcpy (c, dev_c, sizeof(int), cudaMemcpyDeviceToHost);

    free(a); free(b); free(c);
    cudaFree(dev_a);
    cudaFree(dev_b);
    cudaFree(dev_c);
    return 0;
}

the error:

DotProductCuda.cpp:27: error: expected primary-expression before '<' token
DotProductCuda.cpp:27: error: expected primary-expression before '>' token

回答1:

The <<< >>> syntax for calling a kernel is not standard C or C++. Those calls must be in a file compiled by the NVCC compiler. Those files are normally named with a .cu extension. Other API calls to CUDA such as cudaMalloc can be in regular .c or .cpp files.

回答2:

It seems the compiler cannot recognize the <<<,>>> syntax. I have no experience with CUDA, but I guess you need to compile this file with a special compiler and not an ordinary C compiler.

回答3:

nvcc uses the file extension to determine how to process the contents of the file. If you have CUDA syntax inside the file, it must have a .cu extension, otherwise nvcc will simply pass the file untouched to the host compiler, resulting in the syntax error you are observing.

回答4:

Maybe you use a host function (printf for example) inside kernel?

来源：https://stackoverflow.com/questions/5986070/error-compiling-cuda-expected-primary-expression